The American Concrete Institute (ACI) has released an article on: “The influence of aggregate and proportions on flowing concrete characteristics.”
The paper, written by David Trejo and Greg Hendrix, looks at issues such as: “Cast-in-drilled-hole (CIDH) piles (that) are often constructed to depths that are inaccessible, and (where) internal vibration is not performed over the length of the pile.”
Because of this, say the authors: “The likelihood of voids occurring increases. Many state highway agencies use inspection pipes to detect if voids are present along the length of the pile. High reinforcement densities and concrete void detection inspection pipes can congest CIDH piles.”
The document goes on to add that: “Although concrete void detection and reinforcement spacing are critical to ensuring adequate CIDH pile structural performance, eliminating concrete voids can also ensure expected performance.”
ACI says that: “This research will assess the influence of coarse aggregate (CA) type and mixture proportions on concrete workability for CIDH pile applications. Results indicate that identifying an optimal paste volume-to-aggregate void ratio (PV/AV) can be used to proportion flowing concrete (FC) mixtures with adequate slump flow and stability. Concrete containing rounded CA achieved higher slump flow values than concrete with crushed CA at the same paste volume. However, increasing PV/AV also decreased stability. Stability was increased by increasing the FA-to-CA ratio (FA/CA).”
More information is available on the website.